I am at my wits end. My desert tortoise (50 year old male) lives outside year round (I'm in Phoenix AZ and have had him 8 years) and has had a normal behaviour of coming out of his den in about April and for the summer comes out daily for his march around the yard, chasing the dogs and chomping on grass. This year has been different - he came out of his den in April - had his normal behaviour for about a month - and since then does not come out of his den unless I put food out on the ground in front of his entrance. He eats and then goes directly back to his den. I have tried to figure out what has changed - we do have a feral (but pretty domesticated) colony of cats in the area - i thought maybe they were bothering him. I put up a trail cam to see if anything was going in or out of his burrow OR if he was coming out and I did not see it. There is nothing to see - no one going in and him not coming out. I have had the vet look at him - eyes are clear and bright, no nasal discharge etc. I have been putting food out about every 3 days to make sure he doesn't starve. My questions are: has anyone had this kind of behaviour before, how long can a tortoise go without eating, or any ideas on how to break this cycle? I appreciate any advice there is!